i think this is a dumm q...

i think tis is a dum question but im gonna ask you guys anyways...

i just noticed that my yz 450f when pinned on the rev limiter it will shoot some fire and sparks out the exhaust thats normal right??


I hope you noticed this while someone else was on the bike, and not ...nevermind. :cry:

Yes, it's normal. Think about what's happening. A rev limiter works by turning off the ignition above a preset speed. As soon as this happens, the bike slows down, whereupon it falls below the rev limit, and the ignition comes back on. The fuel system was working just fine during this little intermission, however, but since there was no spark, the fuel that was delivered to the cylinder didn't burn and ended up in the exhaust. When the lights came back on, the flame from the once again running engine ignited the fuel in the exhaust pipe, creating your fireworks display. This is why, BTW, rev limiters on electronically fuel injected engines always cut the fuel off, rather than the spark. Taking this approach prevents the flames and popping, but it can't be done with a carb.

hahahah thanks!!

Also if you run them rich a nice flame will shoot out as well.

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